Stoker control



July 25, 1944.

W. W. HALLINAN STOKER CONTROL Filed Dec. 10, 1941 3 Sheets-Sheet l M M y@ July 25, 1944. w. w. HALLINAN 2,354,517

STOKER CONTROL Filed Dec. 1o, i941 s sheets-sheet 2 July 25, 1944. w. w. HALLINAN sToKER CONTROL Filed Dec. 1o, 1941 5 Sheets-Sheet 5 INSS lPatented July 25, 1944 UNITED STATES PATENT CFFICE vstroken coN'rnoL william w. Hallman, Mendota, nl. Appiicaupn December 1 0, 1941, serial No. 422,400 l12 claims. (ci. 11o-s2) The present invention relates to stoker controls, and is particularly concerned with ime.

proved systems anddevices for controlling the operation of coal stokers in such manner as to utilize the coal more eillciently land to reduce temperature over-run to a minimum. A

One of the objects of the invention is the provision of an improved controlling unit for controlling and actuating the gears of the coal feed ,and the supply of air for combustion, which is adapted to permit the independent adjustment of rates of feed of air, both of which may be separately and independently adjusted.

Another object of the invention is the provision v'of an improved stoker controlling unit of the class described, which is simple, sturdy, capable of being adjusted at any time, whether operating lor, not operating, and adapted to be used for a long period of time without any necessity for repair.

Another object is the provision of an improved stoker controlling system which is adapted to eliminate ltheuse of deep fuel beds and to'regulate the coal feed and the air according to the steam pressure or bonnet temperature.

Another object of the invention is the provision of an improved air conditioning' and heating unit and controlling system whichis adapted to eliminate the room temperature over-run above the thermostat setting that is commonly present in the stoker fired units ofthe prior art, thus conserving fuel and raising the overall eiliciency of the heating unit to almaximum.

Another object of the invention is the provision of an improved heating system which is adapted to operate at a high rate of fuel and air feed when the bonnet temperature or steam pressure is below a predetermined value and which is also A 'adapted, as soon as the steam pressure or bonnet temperature reaches such value, to change the fuel feed and air supply in such manner that air will continue to be supplied to burn up the ex cess fuel that has been forced into the fire pot on high feed, thus maintaining eilicient combuspreviously supplied has been burned up and the ilre bed is reduced to a minimum depth, unless the steam pressure or bonnet temperature drops below the -predetermined minimum again, `in which case the stoker is red at high coal and air feed.

Another object of the invention is the provision of an improved air conditioning and heating unit and'controlling system for it, bymeans of which rthe fuel feed maybe cut o i"Y before the room thermostat is satisfied and the furnace operated at reduced combustion air supply, in order to coning an overrun of the thermostat setting and a stopping of the burner by the thermostat Awhen tion without excessive coal feed until the fuel there is a large fuel bed in the furnace.

This large fuel bed produces smoke and wastes the fuel at this time because the combustion air is also shut off in the devices of the prior art, when the fuel feed'is stopped.

Anotner'object of the invention nis the prop vision of Y an improved controlling system for stokers which so controls the combustion that coke trees are fully consumed when a cokingl fuel is used.

Another objectof the invention isthe provisionv of an improved stoker controlling system in which the same'motor may be used for driving the air circulating blowers for theV air which is discharged into the space to be heated and for the air of combustion and in which the supply oi' air for combustiongis not completely shut oi, but mayV be merely reduced-so that whenever the motor is operating, the fuel bed in the furnace is still provided with a. reduced supply ofair to reduce smoking and to produce a more perfect combustion.

Other objects and advantages of the invention willl be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the drawings accompanying this specication, of which there are three'sheets,

Fis. 1 is a diagrammatic elevational view of the stoker controlling system embodying the invention; f.

Fig. 2 is a top plan view of the motor and its driving connections, which -controls and actuates the devices for regulating the coal feed and the airsupply;

Fig. 3 is a sectional View, taken on the plane of the line 3-3 of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a fragmentary sectional view, taken on the plane of the line 4--4 of Fig. 2, looking in the direction of the arrows;

Fig. 5 is a fragmentary sectional view, taken on the plane of the line 5-5 of Fig. 2, looking in the direction of the arrows;

Fig. 6 is a fragmentary sectional view, taken on the plane of the line 6,-6 of Fig. 1, looking in the direction of the arrows.

The present controlling devicesand controlling system is adapted to be used in connection with the combined air conditioning and heating unit disclosed in my prior application, Ser. No. 346,763, filed July 22, 1940 and issued June 29. 1943, as Patent No. 2,323,034; and the present controls may be substituted for those which are disclosed in that application.

In some embodiments of the invention the same driving motor may also be used for driving the blower which circulates the air throughv devices have been omitted, and the motor is dis-V closed as actuating the blower for supplying the air'of combustion and driving the gears which actuate the coal feed.

Referring to Fig. 1, this motor is indicated by the numeral I0, and its shaft II may project from both ends or the purpose of driving a blower and impeller carried in a blower housing at one end and for driving the coal feed from the other end ofthe shaft.

For this purpose the shaft I I carries a V pulley I3 at its right end, which drives a pulley I4 by means of a V belt I5, the pulley I4 being mounted on a driven shaft I6 extending into the gear housing I1.

'I'he gear housing I1 contains any standard form of speed reduction gears connecting the shaft I6 with the driving worm screw of the form conveyor in the conveyor tube of the Stoker.

-The speed of operation of the feed screw is determined by the position of the shaftl 9, which has the usual adjustments, as indicated, for permitting the drive of the screw at a number of different speeds from zero, indicating no drive, to

. speed No. 4.

This mechanism may be so adjusted that the controlling system can drive the screw at high feed or low feed, and the rate of speed is conltrolled by the angular position of the shaft I 9.

. crank arm 20, which is pivotally connected at 2| to a connecting rod 22. The connecting rod 22 may be pivotally connected to a coal feed lever 23 at the point 24 above and behind the motor 25, which controls and actuates the coal feed and air controlling devices.

The blower housing I2 may have its inlet l0- cated at 26, surrounding the shaftsII, and the inlet 26 may be connected to a pipe 21, open at its lower end 28, but adapted to be controlled by a butterfly air valve 29. The butterfly valve 29 is carried by a shaft 30, having a crank arm 3| located outside the pipe 21, and the crank arm 3| is pivotally connected at 32 to a connecting rod 33, comprising two sections slotted and .se-

- cured together by bolts 34 so that the connecting rod is of adjustable length.

The connecting rod 33 has its opposite end pivotally connected by means of a rivet 35 to an air supply lever 36 (Fig. 3), also actuated and controlled by the motor 25.

Referring to Fig. 1, the motor 25, which is seen in the diagram above the motor I0, is actually located behind the face plate 31 of Fig. 1,

the axis of its shaft being indicated at the screw One of the most important features of the invention comprises the controlling unit, details of which are shown in Figs. 2 to 6, by means of which the ranges of movement of the coal feed control lever and the air feed control lever may be independently adjusted and independently controlled and by means of which the rates of feed of air and coal may be set for a predetermined high feed and a predetermined low feed,. and for complete cut-off of the coal feed.

The present controlling arrangements are adapted to be used not only for the air conditioning and heating units shown in my prior application, above mentioned, but also for stokers which are installed in old furnaces, or boilers.

When these controlling arrangements are used in old furnaces, the coal feed would not be completely cut off, but would be merely reduced from high 'feed to low feed, such as a No. 4 feed on high to a No. 1 feed on low.

In other embodiments of the invention the coal feed may be completely out off when the air feed is cut to a minimum. This may be accomplished by setting the lower range of movement of the coal feed controlling lever at zero, a zero coal feed indicatingv zero speed of the operating screw, or no feed at all.

The motor 25 may comprise an electric motor of the type adapted to be energized at volts A. C. from the two conductors 40, 4 I, which enter from the left of Fig. 1, and the windings of the motor generate a low voltage, such as, for example, 24 volts, which are impressed upon the circuit comprising the three conductorsv 42, 43, 44, emerging from the right side of the motor 25, Fig. 1.

When the motor is energized from the conductors 40, 4I, its direction of rotation is controlled by the single pole double throw switch indicated at 45, which has the movable switch arm 46 connected to the conductor 43.

The movable switch arm 46 is adapted to contact with one or the'other of two fixed contacts v 41, 48, but is always in one or the other of the closed contact positions.

The shaft of the motor 25 is adapted to rotate in one direction when the contacts 46, 41 are closed, and in thev opposite direction when-the contacts 46, 48 are closed.

Referring to Figs. 1 to 4, the Stoker motor I0 may be mounted upon a metal plate 49, which is carried by the gear housing l1; and the control motor 25 may also be mounted on the lower side ofthe plate 49 (Fig. 2) by means of a plurality of screw bolts 50 and spacers 5| of suflicient length tolocate the shaft of the'motor at the desired level. v

The controlling unit has a depending face plate 31, which is secured to the supporting plate 49 by a backwardly turned attaching flange 52 and screw bolts 53, and the shaft v54 of the motor 25 is axially located with respect to an aperture v,

for receiving the adjustable stop members 66, 6I..

These stop members are identical in construction, and each may consist of a sheet metal angle bracket 62 and a thumb screw 63. The thumb screw 63 has a knurled cylindrical portion 64 and a threaded shank 65, the shank passing through the slot 59.

The sheet metal angle bracket 62 has a horizontal flange 66 and a vertical flange 61. The vertical flange 61 slidably engages the back of the face plate 31 during the adjustment of the stop, and it prevents rotation of the angle bracket 62. The horizontal flange 66 engages on the upper side ofl the flange 56, and it is preferably welded, soldered, or otherwise secured to a nut 66.

The threaded aperture of the nut 68 registers with an aperture in the flange 66. The nut 68- the lower side of the flange 56. Thus the stop members may be slidably mounted in thef'slot 58, the shank 65 being in the slot, the head below it and the nut above it.

Either stop member 66 or 6| may be loosened by turning its thumb screw 63 counterclockwise so that the stop member may then be slid into the desired position, and it may be secured by turning the thumb screw in a clockwise direction until the screw a'nd nut clamp the flange 58 above and below theslot 59.

The face plate 31 is preferably provided with indicia on its face adjacent the slot 56, suchas Ain Adj., indicating air adjustment. At the ends of the slot there maybethe words Low and Highen Thus the left end of the slot 56 corresponds to the low adjustment for air supply, andthe right end of the slot 56 corresponds tothe high air `feed adjustment.

The vertically extending flanges 61 of the two stop members 60, 6I are long enough to extend over the opening of the slot 56, asseen in Fig. 1,

and to engage the axially turned"`end 1,0 of the air control levez 36, which is so located that it projects into the slot 56.

The range of movement of the air control lever 86 is thus determined by the location of the stops fully closed position where the butterfly valve is transverse to the pipe 21. For this-purpose it is necessary that the stop supporting slotl 59 be of still ,greater length than the arcuate slot 56 in order to provide yspace for sitions of the gears, which haveto be in a definite -A the location of the flanges 61, shanks 65, etc. oi' the stop members 60, 6 I.

At its upper en d the face plate 31 has the arcuate slot 51, previously described. This slot is provided with the stop members 1 I, 12 (Fig. 1). As these stop members are of slightly different construction, shown in Figs. 2 and 6, the slot 51 does not have its sides formed of simple curved lines, having their center at the axisof the shaft 54. Instead, the borders of the slot 51 comprise a plurality of circular grooves 13 on-both sides of the slot, the circular grooves being so arranged that ltheir walls form parts of a circular recess adapted to receive the cylindrical bodies of the stop 1|, 12. y I

Thel face plate 31 preferably. carries on its back side an auxiliary plate 14, which may be semiclrcular 'in plan, and which may be secured in place by a pair of rivets or screw bolts 15 passing through plates 14 and 31.

Auxiliary plate 14 is for the purpose of supporting the stop members 1 I ,"12, and ithas an arcuate slot 16 similar in shape to the slot 56, with concentric sides formed on curves having their center on the axis of the motor shaft 54.

The stops 1I, 12 may be identical in construction, and the stop 12` is illustrated in detail in Fig. 6. It comprises a cylindrical head 11, the outer surface of which is knurled so thatit may be grasped bythe thumb and foreflnger. The head 11 carries a cylindrical shank 16 of reduced size adapted to pass the slot 16, in which the shank is slidably mounted.

The shank 18 carries a washer 1 6 adjacent the stop plate 14 and a compression coil spring 66, which engages another washer I8|, heid in place by a cotter pin 62 passing through the shank 16.

'I'he spring 80 constantly urges the shank 16 toward the left and draws the cylindrical head 11 of the stop member into one of the recesses formed by the curved grooves 13. The stop memgrooves 13.

With the stop member in this axial position, its shank may be caused to slide in the arcuate groove 16 until th'e cylindrial member 12 registers with another of the small circular grooves in the scalloped slot 51. The circular grooves in this scalloped slot 51 are indicated by the numerals 0, 1, 2, 3, and 4; `and the coalr feed lever 23 has an axially turned extension 63 (Fig. 2) which projects into the two slots 51, 16 and engages the side of thecylindrical head 11 of. the stops 1l, 12.

The adjustment therefor is indicated not by the location or registry of the stop with a number, but by the vspace adjacent to ,the stops-1| or 12, in which the extension 8l of the coal feed lever 23 is located when it engages one or the other of these stops. Thus the adjustment for coal feed in Fig. 1 is from zero, or "no feed tol the high feed, No. 4; and at the moment the coal feed lever has its end 63 located at high feed,A

position.

Therefore, the stops 1|, 12 for the coal feed the circular recesses formed by the circulargroove 13.

The actuating levers for the coal and air feed control, which are the coal feed lever 23 and the air feed lever 36, are adapted to be independently driven from the motor shaft 54. For this purpose one of them is driven by means of a spring connection, and the spring is weaker than the torque of the motor, and the other is driven by means of a clutch connection, Which permits the motor shaft to drive on past, after the latter has engaged its stop.

The shaft 54 may be threaded at its end and adapted to receive a hub member 85, which has a centrally located threaded bore 86 for the shaft 54. At its other end the hub member 85 has a reduced cylindrical extension 81, provided with a radially inwardly extending slot 89 (Fig. 4) communicating with an axially extending circular bore 90.

A spiral spring 9| may have its inner end vhooked backwardly at 92 and cylindricallyl curved at 93 to engage the side of a pin 94 driven into the bore 90. Thus the pin 94 secures the inner end of the spiral spring 9| to the hub 85.

The outer end of the spring 9| is provided with a pair of outwardly turned ange portions 95, 96 separated by a slit 91. fixedly mounted upon a cylindrical ferrule 99, which has a cylindrical aperture for engagement on the reduced cylindrical portion 81 of the hub 85.

The ferrule 99 comprises a tubular member having an annular flange |02 at its inner end, and la brass washer |03 may be interposed between that end of the ferrule 99 and the annular shoulder |04 on the hub 85.

The spring cage 98 comprises a substantially circular plate, having a centrally located bore |05 for receiving the ferrule 99, and having a plurality of laterally turned flanges |06 at its periphery, the flanges |06 extending axially of the shaft 54 outside the spring 9|. A

Any or all of the flanges |06 may be provided with a slot |01 (Fig. 4) for receiving radially turned flanges 95 and 96 of the spring 9|. The slot |01 may be made slightly wider at |08 so that the narrow flange 96 may be bent over to engage the shoulder |09 in the slot |08, thus preventing the spring from moving axially out of the slot |01.

The coal' feed lever 23 comprises a metal bar,

the body of which is provided with a circular bore ||0 for receiving the ferrule 99. The lever 23 extends upward and downward from the ferrule 99, and may be secured by a through screw bolt Fig. 2), to the spring cage 98. The screw bolt passes through the lever 23 and A spring cage 98 is is threaded into a threaded bore in the spring cage-98.

As thespring cage has its laterally turned flange secured to the outer end of the spiral spring 9|, the lever 23 is'adapted to be driven by the shaft 54 through the intermediary of the spiral spring 9|. At its lower end the lever 23 is bent diagonally under the spring 9|, and' it extends backward horizontally under the motor 25 and upwardly at I2. It is pivotally connected to the connecting rod 22 at 24.

At its upper end the coal feed lever 23 has the axially turned stop extension 83, previously described, forengaging the stop members 1 12.

The hub member 85 supports, by means of a screw bolt 3, another tubular extension ||"4, forming part of a clutch. The tubular extension ||4 may comprise a cylindrical metal member provided with an axially extending circular bore |5 and with the radially extending clutch flange ||6 at its inner end. Next to the clutch flange ||6 there is 'a cylindrical body portion ||1 of slightly larger size than the cylindrical body ||8 to provide a support for the air control lever 36.

The enlargement ||1 is slightly shorter in an axial direction than the thickness of the air control lever 36, as will be seen by the clearance at I9 in Fig. 5.

The air control lever 36 may comprise a bar of metal, having at one end a circular bore |20 for receiving the cylindrical enlargement ||1. In orderto bring the other end of this lever into the proper plane, the lever is provided with an offset at |2|, and it is pivotally secured to the connecting rod 33 by means of the rivet 35. Its extreme lower end is laterally turned, as indicated at 10; and it projects into the arcuate slot 56 for engagement with the stop members 60, 6|.

A spring lock washer |22 is located between thev extension ||4 and the ferrule 99, and a relatively large washer |26 is located between the head of the screw bolt 3 and the end of the extension ||4. f

A helical coil spring |24 is compressed between the washer |26 and another steel washer |25, which engages the Side of the air control lever 36. The annular flange ||6, air control lever 36, and washer |25 comprise lthe parts of a clutch, the pressure of which is determined by the pressure of the coil spring |24. This clutch permits the air control lever 36 to stop when its end 10 engages either of the stop members 60 or 6|, but the slippage of the clutch also permits the motor shaft to continue to turn.

Thus the setting of the air control stops 60, 6| does not stop the shaft of the motor 25, and the air control stops-may be located at any desired point without affecting the further movement of the motor shaft in the regulation of the coal feed.

The coal feed lever 23 is driven by the shaft 54 of the motor 25 through the intermediary of the spring 9|, which is weaker than the torque of the motor. This means that if the stop extension 83 of the coal feed lever 23 strikes one of the stops 10 or 1|, this does not necessarily prevent the motor shaft 54 from rotating farther because the spring 9| will give. The motor shaft continues to rotate while still Ydriving the air feed lever 36 until it strikes its stop, and thereafter the motor shaft may rotate even farther until the tension of the spring equals the torque of the motor.

The spring 9| serves also to relieve the shockl in the stoppage of the rotor of the motor and to effect a definite stoppage of the motor, although the motor is of a type which has a high inductancey and cannot be damaged by the mere andaI predetermined high air feed, as well as a predetermined low coal feed and a predetermined high coal'feed.

of motor l0, whidilfis connected in As long as the blower is operating there will be some air fed to the re pot, even at low feed.

Referring to Fig. l, the controlling system in which this unit |00 is preferably employed, is there illustrated by means of a wiring diagram |21. In this diagram the supply conductors are controlled by a double pole single throw switch |28, and they comprise the ordinary 110 volt 60' cyclev A. C. lighting circuit. Of the two conductors |29 and |30, one is usually grounded, and it may comprise the conductor |29, the conductor |30 being called the hot line conductor. The hot line conductor |30 mayy extend to one of the contacts |3| of a thermostatic limit switch |32, the other contact |33 of which is connected by a conductor |34 to the terminal |35 of a relay` The conductor |29 leads to the terminal |35 of the relay box, which is also connected to the conductor 4| leading to the motor 25. The conductor 40 from the motor 25 leads to the terminal |31^of the relay box.

The stoker motorv i0 is connected in parallel with the motor 25 of the control unit by means of the conductors |38 and |39, which are connected to conductors 40 and 4|, respectively.

The relay box may contain .a transformer |4|, the primary |40 of which is connected by conductors |42 and |43 to terminals |35 and |36. A`

synchronous clock, indicated at |44, drives a cam for actuating a time switch |45, which has one terminal connected by the conductor |46 to the secondary |40a. The other terminal of the switch |45 leads to the coil .|41 of a relay |48 adapted to control the contacts of a switch |49. 'I'he contacts of switch |49 'are connected by conductors to the terminals |35 and |31. Thus the relay |48 controls the connection of the conductor 40 to the conductor |34. That is the hot side of the line, the grounded sideaof the line |29 already being inv connection with the conductor 4|. Thus the relay |48 coni4 trols the operation of the motor 25 and also that parallel with the motor 25. f.;

This control, however, is effected through the limit switch |32, and the relay cannot turn on either of these motors when .the limit switch is opened.

Thesynchronous clock |44 is connected by conductors to the terminals |35 and |36 so that it is also driven directly from the line through the limit switch |32. The purpose of the synchronous clock |44 andtime switch |45 ,is to 'serve as a pilot for turning on the coal feed and air feed periodically at intervals whichare sufii- 1cilentlyshort to insure the mantenance,of a

The pilot cannot, however, turn on the,coal and air feed when the limit switch is open, Xhtich would be when the furnace is already too the rooms to be heated, and it comprises a thermostatic switch, having a. thermostat |51, movable contact |52, and the fixed contact |53. The xed contact |53 is connected by the conductor |54 to a terminal of the relay box, Which leads position of the shaft I9, which controls the speed may be closed either by the time switch or the room thermostat, and in the latter case the control by the room thermostat is also subject to the limit switch |32.

The operation of the control system is as follows: f

There are three general types of heating plants in which the present control units and system may be used. When the heating plant is a hot air furnace, the limit switch |32 and single pole double throw switch would be thermostatically actuated switch members, including anystandard type of thermostat.

The switches |32 and 45 would -be disposed in the bonnetof the furnace, and would be actuated when the bonnet reaches the proper temperatures.

When the heating plant comprises a steam or 'A vapor installation, the switches |32 and 45 may be actuated by pressure responsive devices which respond to the pressure 'in the boiler, and these devices would lhave their pressure responsive bellows'located inside the boiler.

When the system is a hot water system, the switches |32 and 45 would be actuated responsive to the temperature of the water in the system at the boiler, and they would comprise thermostatically actuated switches, with the thermostat located to be heated from the water of the boiler.

The system is illustrated with the coal feed on high at No. 4 in Fig. 1 and the air adjustment on high at the lower right of Fig. l. The air damper is, therefore, completely open, and the angular reduction gears, is in such a position that coal is being fed at the highest rate, indicated by the numeral 4.

The switch |28 is, of course, closed in order to energize the electrical system. Suppose, for -example, the installation is being used on a steam oiler. The operating switch 45 will be set to ut the coal and air feeds from high to low when the steam pressure reaches three pounds on an installation designed to operate from zero to ve pounds. y

yThe contacts 46, 41 are the high contacts, and they are closed in Fig. 1, because at the present moment the steam pressure is below three pounds.

The room thermostat |50 is located in one of Thus the low voltage circuit` in the relay box As soon as the steam pressure reaches three pounds, the high contacts will be opened and the low contacts 46 and 48 will be closed, but in the meantime the armature and shaft of the small motor 25 are in such position that they have moved the coal and air feeds to high. f,

It should be understood that this high posi-A tion of air and coal feed is-not any arbitrary or fixed value, but it is the higher of the two ranges of coal feed or. air feedas determined by the 'setting of the stops. coal feed, No. 3, or even No. 2.-

The present device may have its coal feed adjustedindependently of the air supply. v

Suppose, under these conditions, the room thermostat |50 shows a demand for heat, and suppOse the high limit switch |32 is closed, as it would be if the boiler had not reached a pressure or temperature exceeding its predetermined value. The room thermostat switch closes upon cooling below a predetermined temperature and' opens when heated. Thus, this room thermostat is open when the room has been heated to the setting of the room thermostat and it closes when the room cools below the predetermined temperature of its setting.

When the room cools below this predetermined The high may be a No. 4

closes, we say that it is demanding heat. Suppose,

for example, the room thermostat demands heat.

Under these conditions the stoker would operate for perhaps ten or fifteen minutes, and the steam pressure would rise to threepounds, at which point the operating switch 45 would open the high circuit, comprising contacts 46, 41, and close the low circuit, comprising contacts 46, 48. This causes the controlling motor 25 to' reverse its direction and move in the opposite direction toits previous movement, thereby changing the coal setting from high to low, and the air adjustment from high to low. The Stoker would then operate on low coal feed and low air feed.

Sometimes after such a cycle of operation the steam pressure will continue to rise to four pounds, and sometimes to five pounds; and this is due to the extra amount of coal which is put into the furnace during the previous cycle, before the limit of three pounds pressure was reached.

This amount of pressure overrun will vary, dem pending upon the length of timethat the stoker has been off and depending upon the question of how cold the furnace is and how cold the outside temperature is, andhow low the temperature is in the house to be heated.

.For instance, if the stoker had been off 'all night, the plant would be cold, thus taking longer to `build up three pounds. It it takes longer to build up three pounds pressure, the stoker would' operate a longer time on high, due to this condition; and it would naturally build up a larger supply of coal in the furnace before the three. pound pressure was reached.

Thus it would follow that, with a greater amount of coal in the furnace when the Stoker t was cut from high to low feed, plus the coal which may continue to be fed into the furnace on the low setting, the furnace might reach the five pound setting on the limit switch.

If this should happen, the limit switch |32 would open and stop the stoker until the steam pressure dropped to four pounds, when it would restart, and then it would naturally be operating on the low coal feed and low air feed setting.

Ordinarily during the day the limit switch setting will never be reached because the stoker will be cut from high to low feed with a small enough fire or fuel bed 'to keep the steam pressure at approximately three to four pounds.

I have found that in most cases the stoker is invariably stopped by the room thermostat being satisfied after the stoker has Vbeen operating on low settings for a long enough period of time to have the fuel or fire bed very low. Thus a saving of from eighteen to thirty-three and one-third percent in fuel is accomplished, and at the same time the room thermostat is not over-run, as is the case with the standard stoker devices of the prior art.

In the prior art devices the feedsI must be high enough to brin'g up the temperature and to maintain the load during the coldest of weather; but this inevitably brings about a temperature overrun at the room thermostat with the devices of the prior art.

As distinguished from this, I have found that the present system will maintain the room temperature of my stoker fired system so uniform that it does not vary one-half degree F. during a twenty-four hour period of operation, while the outside temperature drops from 44 degrees F. to 12 degrees F. below zero.

The same vroom thermostat which. with the devices of the prior art, could not hold the room or laboratory within five degrees F. of the setting of the room thermostat, was adapted, with the present system, to maintain the temperature substantially constant, with a variation of no more than one-half degree F.

Temperature over-runs were eliminated because the green coal forced in on the high fire is substantially all burned up just before the thermostat is satisfied on the low firing. Suppose, for example, the stoker has been cut to low feed and the steam pressure drops to one point, but the temperature setting of the room thermostat has not yet been reached. Then the high contacts of the operating switch 45 will again be closed. This will start the small motor in the opposite direction, bringing the coal and air feeds to high position, where they will remain until the three pound pressure has again been reached. At this point the operating switch 45 will again close the low contacts and operate the motor to set the coal and air feed on low until the pressure has dropped again to about one pound.

Thus the stoker is ordinarily between three and one pound pressure at all times except in the case of the cold boiler at the start, in which case the high or' five pound limit switch setting might'be reached.

When the system is installed in a -hot air furnace,- the limit switch |32 would comprise a thermostatic switch, having a setting of, for' example, 350 degrees F. The operating switch 45 in the plenum chamber would be a thermostatic switch, having a setting of degrees F. This would mean that -if the temperature exceeded 150 degrees F,., the high contacts 46, 41 would be opened; but if the temperature decreased below 150 degrees F., the low contacts 46, 48 would be opened.

I desire it to be understood that the temperatures which are used as examples in this description are merely for the purpose of illustration, and the present device may be arranged to operate at any temperatures suitable for stoker red heating plants.

The advantages of my summarized as follows:

1. Temperature overruns in the room to be heated are substantiallyv eliminated, and the temperature is maintained within one-half degree of the room thermostat setting.

2. There is a substantial saving of from eighteen to thirty-three and one-third percent of fuel because the green fuel that is forced in on high feed is fully burned up afterward on low feed.

3. Less electric current is consumed, as the coal feed and air feed require less power when they are operated at low feed, as in devices of the prior art.

4. Coke trees or large shafts of coke are eliminated due to the cutting of the coal feed from high to low, during which low feed they are consumed.

5. The hard clinkers which usually form ,in the devices of the. prior art over the burner and around the retort are broken upand moved over t0 the side or top of the fire because such clinkers as are formed on high feed are broken up by the continuance of the feed of fuel on low, and there is no opportunity for the clinkers to cool and settle down over the burner, as they do in the devices of the prior art, where coal is fed at high feed and then completely cut. oil'.

system may then be 6. The stoker retort will last indefinitely, or its cause .when the burner is stopped there is no large hot mass directly over and around the retort. The coal iiredin the retort and above it has been broken up into small pieces and cooled when operating onv low feed, and the continuance of the flow of the cooling air has also served to keep the retort cool.

7. The present control unit permits the independent setting of high air feed and low air feed, and high coal feed and low coal feed, so that the system is flexible and adaptable to all kinds of temperature conditions and all kinds of heating plants.

While I have illustrated a'preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. A controlling unit for stokers, comprising a support, an electric motor carried by said support and having a driving shaft, a coal feed control member rotatably mounted on said shaft and `connected to said shaft through the intermediary of a spring, and a pair of adjustable stop members carried by said support and disposed in the range of movement of said coal feed control member, whereby the stops may be adjusted at two different rates of coal feed and the motor may operate said coal feed control member to move it to one or the other of said coal feed positions.k

2. A controlling unit for stokers, comprising a support, an electric motor carried by said support and having a driving shaft, a coal feed control member rotatably mounted on said shaft and connected to said shaft through the intermediary of a spring, and a pair of adjustable stop members carried by said support and disposed in the range of movement of said coal feed control `member, whereby the stops may be adjusted at adapted to be drivenin either direction and having a drive shaft, a clutch carried by said drive shaft and an`air feed control memberl mounted .on said clutch to be releasably driven by said drive shaft, and a pair of stop members carried by said support for engagement with said member whereby the motor may drive said air feed control member to either of two air feed control positions.

5. In a controlling unit for stokers, the combination of a support with an electric motor adapted to be driven in either direction and having a drive shaft, a clutch carried by said drive shaft and an air feed control member mounted on said clutch to be releasably driven by said drive shaft, and a pair of stop members carried by said support for, engagement with said member whereby the motor may drive said air feed 'control member to either of two air feed control positions, said support having an arcuate slot, and said member having an extension in said slot. f

6. In a controlling. unit for coal stokers, the combination of a support with a driven shaft rotatably mounted upon said support, electrically controlled driving means carried by said support for driving said shaft, a feed controlling member for controlling the feed to the Stoker of one of the elements of combustion, a pair of adjustable stop members for said feed controlling member, said stop members being carried lby said support and operative mechanical connecting means for driving said feed control member from said shaft and permitting relative movement of said member and said shaft when the motion of said feed control member is opposed by a stop, and means for adjustably securing said stops at an'y of a multiplicity of different -positions on said suptwo different rates of coal feed and the motor may operate said coal feed Control member to move it to one or the other of said coal feed positions, said stops being movably mounted in an arcuate slot, and said member having an extension extending into said slot.

3. A controlling unit for stokers, comprising a support, an electric motor carried by said support and having a driving shaft, a coal feed control member rotatably mounted on said shaft and connected to said shaft through the intermediary of a spring, mem-bers carried by ,said support and disposed in the range of movement of said coal feed control member, whereby the stops maybe adjusted at two dierent rates of coal feed and the motor mayl operate said coal feed control member to move it to one or the other of said coal feed positions, said stops being movably mounted in an arcuate slot, and said member having an extension extending into said slot, each of said stops comprising a spring pressed plunger and said slot having a plurality of recesses for receiving a part of said plunger, whereby the stops are held in any of a plurality of predetermined gear positions.

and a pair of adjustable stolv 4. In a controlling unit for stokers, the com' for driving said shaft, a

bination of a support with an electric motor port whereby the upper and lower limits of motion Vof said feed control member may be independently and separately adjusted.

7. In a controlling unit for coal stokers, .the combination of a support with a driven shaft rotatably mounted upon said support, electrically controlled driving means carried by said support for driving said shaft, a feed controlling member for controlling the feed to the Stoker of one of the elements of combustion, a pair of adjustable stop members for said feed controlling member, said stop members being carried by said support and operative mechanical connecting means for driving said feed control member from said shaft and permitting relative movement of said member and said shaft when the motion of said feed control member is opposed by a stop, and means for adjustably securing said stops at any of a multiplicity of different positions on said support whereby the upper and lower limits of motion-of said feed control member may 4be independently and separately adjusted, said operative mechanical connecting means comprising a clutch interposed between said feed control member and said shaft.

8. In a controlling unit for coal stokers, the

combination of a support with a driven shaft rotatably mounted upon said support, electrically controlled driving means carried by said support feed controlling member for controlling the feed to the stoker of one of the elements of combustion, a pair of adjustable stop members for said feed controlling member, said stop members being carried by said support and operative mechanical connecting means for driving said feed control member from said shaft and permitting relative movement of said mem- -ber and said shaft when the motion of said feed control member is opposed by a stop, and means for adjustably securing said stops at any of a multiplicity of different positions on said support whereby the upper and lower limits of motion of said feed control member may be independently and separately adjusted, said operative mechanical connecting means comprising a spring interposed between said shaft and said feed control member.

9. In a controlling unit for coal stokers, the combination of a support with a shaft rotatably mounted on said support, electrically controlled driving means for said shaft, a pair of feed control members mounted on said shaft, a stop carried by said support for determining one of the limits of range of movement of said feed control members and operative mechanical connecting means between said shaft and each of said members for driving said members from said shaft except when'the motion of either of said members is opposed -by said stop, and means for adjustably securing said stop in any of a plurality of different positions whereby one of the limits of range of feed of said feed control members may be independently and separately adjusted.

10. In a controlling unit for coal stokers, the combination of a support with a shaft rotatably mounted on said support, electrically controlled driving means'for' said shaft, a pair of feed control members mounted on said shaft, a stop carried by said support for determining one of the limits of range of movement of said feed control members and operative mechanical connecting means between said shaft and each of said members for driving said members from said shaft except when the motion of either of said members is opposed by said stop, and means for adjustably securing said stop in any of a plurality of different positions whereby the limits of range of feed of said feed control members may be independently and separately adjusted, one of said operative mechanical connecting means inmef 'lo 'nee .c mein .bias in J n nos effi ,areiloe roi thm :milicianos nevera evitarse gni'alln'iecg ma Lesioni oi'lieeis .ne filas .manqua ,e in nomadic?" cluding a clutch interposed between said shaft and one of said feed control members.

11. In a controlling unit for coal stokers, the combination of a support with a shaft rotatably mounted on said support, electrically controlled driving means for said shaft, a pair of feed control members mounted on said shaft, a stop car\ ried by said support for determiningone of the limits of range of movement of said feed control members and operative mechanical connecting means between said shaft and each of said members for driving said members from said shaft except when 'the motion of either of said members is opposed by said stop, and means for adjustably securing said stop in any of a plurality of different positions whereby one of the limits of range of feed of said feed control members may be independently and separately adjusted, said operative mechanical connecting means including a spring interposed between said shaft and one of said feed control members.

12. In a controlling unit for coal stokers, the combination of a support with a shaft rotatably mounted on said support, electrically controlled driving means for said shaft, a pair of feed control members mounted on said shaft, a stop carried by said support for determining one of the limits of range of movement of said feed control members and operative mechanical connecting means between said shaft and each of said members for driving said members from said shaft except when the motion of either of said members is-opposed by said stop, and means for adjustably securing said stop in any of a plurality of different positions whereby one of the limits of range `of feed of said feed control members may be independently and separately adjusted. said operative mechanical connecting means including a spring interposed between said shaft and one of said feed control members, and including a clutch interposed between said shaft and the other of said feed control members.

WILLIAM W. HALLINAN. 

